Electrostatic cleaning method and apparatus



April 12, 1966 R. GALLINO 3,245,835

ELECTROSTATIC CLEANING METHOD AND APPARATUS Filed 001:. 8, 1965 ATT NEYSUnited States Patent Jersey Filed Oct. 8, 1963, Ser. No. 314,731 Claims.(Cl. 134-1) The invention relates to a method and device for removingdirt from the surface of paper being processed, for example, in printingpresses and the like.

In the printing trade, surface dirt which becomes attached to the paperstock is a considerable source of annoyance. The dirt or impurity mayoriginate from the paper stock itself, from its packing, or may simplybecome attracted from the ambient atmosphere owing to static electricityelfects.

Various complicated methods and devices have been devised for reducingor removing surface dirt of this kind. These include complex vacuumdevices and air blowers, electric generators, and the like. (Hithertoknown solutions either require a source of carefully adjustable electriccurrent, or they involve intricate mechanical-electrical devices whichare costly and tedious to operate.

It is an object of the present invention to provide a method and devicefor removing or at least substantially reducing surface dirt in theprinting trade and in similar applications, e.g., mimeographing andcoating.

It is another object of the invention to avoid the drawbacks ofpreviously known methods and devices, such as high expense, andcomplicated installation and use.

According to the invention, a film of plastic is laid across the paperbeing processed, either before or after the sheeting operation. The filmis adapted to build up a static charge by frictional contact with themoving paper. The static charge produced by this expedient attracts theparticles of dirt which are attached to the paper. Since the plasticfilm tenaciously clings to the traveling web, the surface dirt iscollected and the printing press is then fed with material free fromimpurities.

In a preferred embodiment, a piece of plastic film is hung above thetraveling paper web so that the static charge develops because of therelative movement between the stationary plastic film and the movingpaper. In another embodiment, supply and take-up rolls of plastic filmare provided in proximity to the paper feed, whereby the film may bemoved in a direction opposite to that of the feed. Upon depletion of thesupply roll, the plastic film can be re-used by switching the empty andfull film rolls.

One of the important advantages of the invention is that the staticcharge continuously regenerates itself by the contact between the filmand the paper. Furthermore, the film can be readily cleaned of theadhering dirt so that re-use is possible without added expenditure ortime-consuming operations. Other objects and advantages of the inventionwill be appreciated and more fully understood with reference to thefollowing detailed description, when considered with the accompanyingdrawing, wherein FIG. 1 is a schematic perspective view of oneembodiment of the device for carrying out the novel method according tothe invention;

FIG. 2 is a similar view of another embodiment of the invention; and

FIG. 3 is a schematic side elevation of a third embodiment of the devicefor carrying out the novel method of removing surface dirt.

In FIG. 1, a continuous paper web 10 is shown passing from theright-hand side of the drawing (supply) to the left-hand side (printingpress or the like). A stationary block 12 is fastened to the machineframe or similar ele- 3,245,835 Patented Apr. 12, 1966 ment, and asupporting rod 14 extends from block 112 above the path of paper '10substantially perpendicular to its direction of travel. A plastic film16 is fastened to rod 14 in any conventional manner so that it hangsdown and engages the surface of web 10. The frictional engagementbetween web 10 and film 16 produces a static charge due to thefrictional drag of the ceramic clay coating on the paper. In operation,the surface dirt adhering to the untreated portion 10a of web 10 iscaught by film 16 due to the static charge. The treated web portion 10b,beyond the range of contact with the film, will thus be substantiallyfree from dirt.

FIG. 2 illustrates another embodiment of the invention. A continuouspaper web 20 passes from the right to the left. Stationary blocks 22 and23 carry rotatable shafts 24 and 25, respectively, which are adapted tohold a supply roll of film 27 and a take-up roll 28. Shaft 25 has apulley 2.1 attached thereto from which it can be driven by conventionalextraneous means (not shown) such as an electric motor. Additionalrotatable shafts 24 and 25', held by stationary blocks 22' and 26,respectively, stretch the film so that an intermediate portion 26remains in intimate contact with web 20. If desired, shafts 24' and 2-5may be biased by conventional means toward the web so that sufficient,adjustable resilience will be provided between the frictionally engagingpaper web and film. When all of the film has been transferred from roll27 to roll 28, the rolls may be interchanged so that the film can bere-used.

A third embodiment of the invention is shown in FIG. 3, wherein a web ofpaper 30 moves in the same direction as a continuous film band 36stretched over rollers 37 and 38 which are rotatably mounted on axles 34and 35, respectively. By conventional means (not shown), film band 36may be :made to run faster or slower than web 30. Adjustment of theengagement between film and paper, as well as regulation of therespective speeds, will alter the degree of dirt removal withinprescribed limits, without physically damaging the paper surface.

Although the second embodiment discloses movement of the paper web andplastic film in opposite directions, the film may move in the samedirection or be stationary, depending upon the speed difierentialdesired between the web and film. Movement in opposite directions hasthe added advantage that accumulated dirt is moved toward the supplyportion of the web, rather than toward the treated, clean portion whereit may adhere to the web again.

The plastic film used in accordance with the principles of the inventionmay the polyethylene, nylon, cellulose acetate, polyvinylidine chlorideor the like. It has to be flexible enough to adhere to the paper web,and smooth enough not to roughen up the surface of delicate printingpapers. In the embodiments of FIGS. 2 and 3, the atmospheric humidityprevailing at the site where the device is used can be elficientlycompensated (for by judicious adjustment of the relative speed betweenthe \film and the paper web.

Experiments have shown that best [results can be obtained by using anylon fabric approximately 1 mil thick with 2 mils of polyethylenecoating on each side.

Although schematically shown in connection with supply means forprinting presses, the invention can be employed with a device attachedto or forming part of paper manufacturing machinery as well. No majorinstallation is required and the inventive device can be added with easeto any existing installation.

The foregoing disclosure relates only to preferred embodiments of theinvention which is intended to include all changes and modifications ofthe examples described within the scope of the invention as set forth inthe appended claims.

What is claimed is:

1. A method [for removing dirt particles from the surface of a web,which when rubbed against a given material produces in the lattermaterial an electrostatic charge attracting dirt particles from the webto said given material, comprising the steps of: applying the end of acomparatively wide film of said given material across the full width ofsaid web, with the sides of said film extending past the side edges ofsaid web; producing relative motion between said web and said film in adirection transverse to the width of said web to rub said film againstsaid web, whereby the static charge produced on said film by saidrubbing causes the dirt particles to leave said web and adhere to saidfilm; and maintaining said film in continuous and intimate contact withsaid Web during said motion so as to capture the dirt particlestherebetween.

2. A method according to claim 1, wherein said relative motion isproduced by holding said film stationary while said web travelstherealong.

3. A method according to claim 1, wherein said relative motion isproduced by moving said film at a speed different from that of thetraveling web.

4. A method according to claim 3-, wherein both said web and said filmmove in the same direction, the speed of said film being greater thanthat of said web.

5. A device for removing dirt particles from the surface of a web or thelike, comprising in combination, a

flexible and substantially smooth film having an end thereof extendingacross the entire width of said web and past the sides thereof, saidfilm being of a material which when rubbed against said web becomeselectrostatically charged to attract dirt particles firom said web,means for producing relative movement between said web and said film, torub the latter over said web in a direction transverse to the width ofsaid web, and means for holding said film in intimate and continuouscontact with said web so that the dirt particles removed from said webdue to the electrostatic charge on said film are trapped between saidfilm and said web.

6. A device according to claim 5, wherein said means for producingrelative motion consists of a structure for moving said web beneath saidfilm and said holding means comprises a stationary rod-like member whichcarries said film and from which said film hangs down into engagementwith said web.

7. A device according to claim 5, wherein said holding means comprises apair of spaced-apart shafts, said film being in the [form of a stripwound on said shafts, and means vfor moving said film strip from oneshaft to the other while contacting said web.

8. A device according to claim 7, wherein said holding means comprises asecond pair of shafts, said film strip being guided between said shaftsof the first mentioned pair over those of the second pair.

9. A device according to claim 8, wherein both said web and said filmare moved in the same direction, the speed of said film being higherthan that of said web.

10. A device according to claim 5, wherein said holding means comprisesa pair of spaced-apart .axles, a roller on each of said axles, andwherein said film is in the form of a continuous endless strip woundaround said rollers.

References Cited by the Examiner UNITED STATES PATENTS 1,947,748 2/ 1934Van Wormer l5308 2,518,384 8/1950 Settergren 15-232 2,894,744 7/1959Schulze 15--1.5 X 3,074,086 1/1963 Remer 151.5 3,099,856 8/1963 Eichornet a1 15l.5 X

, FOREIGN PATENTS 1,175,749 11/1958 France.

601,456 8/ 1934 Germany.

47,998 6/1930 Norway. 340,456 9/ 1959 Switzerland.

CHARLES A. WILLMUTH, Primary Examiner.

WALTER A. SCHE'EL, Examiner.

1. A METHOD OF REMOVING DIRT PARTICLES FROM THE SURFACE OF A WEB, WHICHWHEN RUBBED AGAINST A GIVEN MATERIAL PRODUCES IN THE LATTER MATERIAL ANELECTROSTATIC CHARGE ATTRACTING DIRT PARTICLES FROM THE WEB TO SAIDGIVEN MATERIAL, COMPRISING THE STEPS OF: APPLYING THE END OF ACOMPARATIVELY WIDE FILM OF SAID GIVEN MATERIAL ACROSS THE FULL WIDTH OFSAID WEB, WITH THE SIDES OF SAID FILM EXTENDING PAST THE SIDE EDGES OFSAID WEB; PRODUCING RELATIVE MOTION BETWEEN SAID WEB AND SAID FILM IN ADIRECTION TRANSVERSE TO THE WIDTH OF SAID WEB TO RUB SAID FILM AGAINSTSAID WEB, WHEREBY THE STATIC CHARGE PRODUCED ON SAID FILM BY SAIDRUBBING CAUSES THE DIRT PARTICLES TO LEAVE